Inverted Metamorphic Solar Cell Fabrication via Surrogate Substrate
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Solution Overview
Problem
Existing methods for manufacturing inverted metamorphic multijunction solar cells face challenges in choosing appropriate materials and fabrication steps, leading to difficulties in producing commercially viable devices with high efficiency and low mass for terrestrial and space applications.
Innovation Solution
A method involving the growth of subcells on a substrate in reverse sequence, using a surrogate substrate and bonding elements to attach a cover layer, and removing the growth substrate to expose the top subcell, while controlling lattice constants and electrical properties through specific reactor conditions and chemical composition.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If conventional manufacturing methods are used for inverted metamorphic multijunction solar cells, then the fabrication process becomes complex and difficult, but the manufacturing precision and commercial viability are compromised
Solution Approach 1:
The patent applies inversion by growing the solar cell subcells in reverse sequence on a surrogate substrate, with the top subcell (highest bandgap) grown first and subsequent subcells grown in descending bandgap order. This inverted growth sequence simplifies the fabrication process by eliminating the need for complex lattice-matching calculations and intermediate substrate transfers, while maintaining high manufacturing precision through controlled epitaxial growth conditions
Solution Approach 2:
The patent uses a surrogate substrate as an intermediary medium that enables the inverted growth sequence. This surrogate substrate acts as a temporary platform that accommodates the reverse-order subcell structure during fabrication, allowing precise control of lattice constants and electrical properties through specific reactor conditions, and can be removed or transferred later in the process
2Loss of energy
If high efficiency is pursued through complex material selection and fabrication steps, then energy conversion efficiency improves, but device mass and manufacturing complexity increase
Solution Approach 1:
The patent achieves high energy conversion efficiency by systematically varying key parameters during the inverted growth process, including lattice constants, bandgap energies, and electrical properties of each subcell. By controlling these parameters in reverse sequence on the surrogate substrate, the method produces high-efficiency devices with simplified fabrication, reducing both manufacturing complexity and device mass compared to conventional approaches
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This approach enables the production of high-efficiency solar cells with improved short circuit current and radiation resistance, enhancing the power-to-weight ratio and efficiency of solar cells for both terrestrial and space applications.
Implementation Method 1
forming a group of discrete, spaced-apart first bonding elements over the surface of the back metal contact; attaching a surrogate substrate on top of the back metal contact using the bonding elements
Data Source
AI summary
A method of manufacturing a solar cell by providing a first substrate; depositing on the first substrate a sequence of layers of semiconductor material forming a solar cell including a top subcell and a bottom subcell; forming a metal back contact over the bottom subcell; forming a group of discrete, spaced-apart first bonding elements over the surface of the back metal contact; attaching a surrogate substrate on top of the back metal contact using the bonding elements; and removing the first substrate to expose the surface of the top subcell.